Alkali-resistant glaze



Patented Jan. 4, 1944 2,338,099 ALKALI-RES ISTAN '1 GLAZE Alden J.Deyrup, Westfleld, N. .L, assignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware No Drawing.Application December 1, 1941, Serial No. 421,245 7 20 Claims.

This invention relates to the decoration of the surfaces of glass andceramic ware by the use of low-melting glazes, which glazes. may be pigmented' and/or opacified. Although generally useful in the decoration ofall types of ceramic surfaces, the invention is especially useful forthe decoration of the surfaces of glassware articles. The inventiondisclosed in this application is in part, a continuation of thatdisclosed in my copending patent application Serial No. 336,415, filedMay 21, 1940, now Patent No, 2,278,868.

The surfaces of glass and ceramic articles are frequently decorated bymelting thereon a glaze composition. This glaze composition is usuallypigmented by the addition of a ceramic pigment, and may or may not alsocontain an opaeifying agent. The glaze composition, which is also termeda color in this art, must be one which will melt and form an adherentcoating at a temperature below that at which softening or deformation ofthe glass or ceramic article decorated would occur. It is in thisspecial field of low-melting glaze or enamed compositions, melting toform a glossy adherent coating generally below 1150' F., particularlyuseful for the decoration of articles of glassware, that the novelcompositions with which this invention is concerned find their principalutility.

The art of decorating glassware by the application thereto of alow-melting glaze composition, ordinarily known as a glaze or color, hasbeen practiced for a number of years. 'Among the glaze compositionssuitable, melting below about 1150 F., it has been customary to employthe silicates and the borosilicates of lead. These compositionsordinarily melt at temperatures below those at which danger of injury tothe glass articles being decorated by softening or deformation wouldoccur. They can therefore be utilized in the decoration of glasswaresurfaces "by melting the glaze compositions thereon. The lowmeltingborosilicates of lead are ordinarily prepared by melting together anoxide of lead, boric acid and silica in such proportions as to yield aglaze composition having a suitably low melting point. The low-meltinglead silicate glazes, which usually have somewhat higher melting pointsthan the lead borosilicates, are usually prepared by melting together anoxide of lead and silica, in suitable proportions, together with analkali metal oxide such as the oxides of sodium, potassium, or lithium.

While the presence of boron in the lead borosilicate glaze compositions,the boron usually being introduced asboric oxideor some compoundyielding boric oxide during the melting such as boric acid, has beendesirable from the point of view of lowering the melting point, its

inclusion has resulted in a substantial lessening in the resistance toacids and alkalies 'of the glaze compositions and of the resultingglossy decorai by the melting thereon of a low-melting glaze tivesurfaces. Various attempts have been made to secure glaze compositionswhich would possess satisfactory low melting points but would,nevertheless, have greater resistance to the action of chemical agentssuch as acids and alkalies. Generally, it has been necessary tosacrifice melting point in order to obtain increased resistance, theresistance of any glaze composition to chemical action ordinarilyincreasing as the fusion point of the composition increases. In ordertoobtain superior resistance to the action of .chemical agents suchas thealkalies, it has been necessary in the art to prepare compositionshaving relatively high melting points, the melting points in someinstances being so high as to prevent or seriously restrict theutilization of the glaze compositions in the decoration of glasswaresurfaces. Glazes, of relatively low melting point, such as some leadborosilicate glazes, on the other hand, are soluble to a substantialextent even in water.

Recently the decoration of glass milk bottle composition has beencommeroial ly practiced to a substantial extent. When glass milk bottlesare returned to the dairy for further use it is customary to wash thesebottles in a hot solution containing considerable quantities of caustic.This alkali has been injurious to the colored decoration on the milkbottles, the usual types of low-melting glazes not possessing sufllcientresistance to the action of alkalies to render the useful life of themilk bottles more than that 'of a relatively few washings. In order toprolong the'activ'e life of these bottles, it has become increasinglyevident that the colored decoration would have-to be secured by the useof a glaze composition having greater resistance to the action ofalkalies than those low-melting glazes now known to the art.

Increased resistance to chemical action, par-- ticularly to the actionof alkalies, must be attained, however, without substantially elevatingthe melting point of the glaze composition applied to the glass bottlesor other glassware. As previously specified, softening of most glasswarearticles occurs at temperatures around 1100 F.,

or even, in some cases, at temperatures below- 1100 R, such as 1000 F.This means that for decorating most glassware surfaces the glazecompositions must possess fusion points not in excess of 1100 F. Glassmilk bottles, because of their substantial thickness, may be regarded asan exception to this general rule, however,'the softening temperature ofsuch milkbottles being frequently inexcess of 1100 F. Accordingly, myinvention includes the preparation of compositions for decoratingglassware which possess fusion points up to about 1150 F., as suchdecorating compositions can frequently be used in the decoration of sometypes of glassware such as glass milk bottles and other articles ofrelatively thick glass. As previously stated, the general resistance ofa glaze for decorating glassware and of the resulting decoration on theglass article decorated increases as the fusion point of the glazecomposition increases.

In my previously referred to copending patent application Serial No.336,415, now Patent No. 2,278,868, I have disclosed low-melting leadglaze compositions of increased resistance to the action of alkalineagents, which compositions are prepared by fusing and fritting a batchmixture comprising lead oxide, silica, boric oxide, zirconium oxide, andone or more of the oxides of the alkali metals having an atomic weightbelow 40. This group of alkali metaloxides includes those of the metalslithium, sodium, and potassium, all these metals having atomic weightsbelow 40. The zirconium oxide is melted into the glaze composition toform a clear homogeneous solution with the other ingredients comprisingthe flux. These glazes are characterized by increased resistivity to theaction of alkalies without undue elevation of their maturingtemperatures. There is, however, a definite limit to the increase in theresistivity of these glazes to alkaline agents that can be securedwithout unduly increasing their coefiicients of expansion. Since theglazes are intended for application to glassware surfaces, thecoeflicient of expansion is fully as important as the melting point(maturing temperature), and increased alkali resistance cannot besecured at the expense of too great an increase in the coefiicient ofexpansion.

The glazes with which this invention is concerned are an improvementover those of my copending patent application, and are characterized byenhanced alkali resistance without sacrifice in maturing temperature andwithout un- 'due increase in the coefficient of expansion.

They are also characterized by improved stability with the cadmiumcolors when red decorative coatings are produced by the use of thecadmium selenide and cadmium sulfoselenide ceramic pigments, as comparedwith enamel compositions now known to the art.

My improved glaze compositions may be prepared from batch compositionsyielding lead oxide, silica, zirconium dioxide, and one or more of thealkali metal fluorides of those alkali metals having an atomic weightbelow 40. This group includes the fluorides of the alkali metalslithium, sodium, and potassium. The refractory .oxide zirconia ismeltedinto homogeneous solution in the low-melting enamel. In addition,there may be present one or more of the alkali metal oxides,particularly the oxides of those alkali metals having an atomic weightbelow 40, and, if desired, boric oxide in amounts up to 10% by weightbased on the total weight of the composition.

Low-melting glazes having this composition are characterized by superioralkali resistance without an unduly great coeflicient of expansion.

Moreover, they possess improved stability with certain types ofpigmentary agents. They are also less susceptible to reduction,darkening, or

blistering by the carbonaceous residues of organic application mediathan are previously known glaze compositions. This is a distinctadvantage when the squeegee process is utilized for applying the glazecomposition to articles of glassware to be decorated, and the superiorstability with the cadmium colors permits'the securement oi brighter andmore satisfactory decorative coatings pigmented to a red or orange colorby the use of cadmium solfoselenide or cadmium selenide ceramicpigments.

Table I summarizes the constituents present in my improved glazecompositions, and the ranges in which those constituents should bepresent under circumstances wherein maximum resistance to the action ofalkaline agents without sacrifice of maturing temperature and withoutundue increase in coeflicient of expansion is essential. l

The zirconia (2102) is melted with the other ingredients of the batch toform a clear homogeneous solution during the preparation of the frit.The alkali metal fluoride is either lithium fluoride, sodium fluoride,potassium fluoride, or a mixture of two or more of these fluorides.Similarly, the alkali metal oxide, which need not be present but may bepresent in amounts up to 5%, is an oxide of lithium, sodium, potassium,or mixtures of two or more of these oxides. As previously pointed out,the alkali metal, whether introduced as fluoride or oxide, or as bothfluoride and oxide, must be one or more of those having an atomic weightbelow 40. It may be remarked that I do not know definitely whether thefluorine introduced is present as lead or al kali metal fluoride, or inthe form of fluosilicate, but it is conveniently given in the calculatedcomposition as an alkali metal fluoride. Boric oxide need not bepresent, but if present the amount will not exceed 10% by weight, basedon the total weight of the glaze composition.

Wide variations of the various constituents of the flux within the aboverange are possible without sacrificing the desirable characteristics ofhigh resistivity to the action of alkaline agents at relatively lowmaturing temperatures. Thus, the zirconium dioxide constituent may beincreased within the range given, generally larger amounts of zirconiatending to increase the resistance of the glaze to the action ofalkalies. However, if

the content of zirconium dioxide is too great, it may interfere with thestability of titanium dioxide when the latter oxide is added as a milladdition during the milling of the glaze compositionin order to functionas an opacifying agent in the decorative coating applied to the articledecorated.

The sum of the alkali metal oxide and alkali metal fluoride contents maybe regulated in order to adjust the coefiicient of expansion of theglaze within any desired range. Increasing the' ratio of alkali metalfluoride content to alkali metal oxide content is beneficial inincreasing alkali resistance, but may somewhat reduce the resistivity ofthe glazes to'the action of acids. A high ratio of alkali metal fluorideto alkali metal oxide is also beneficial to the stability of somepigments, such as the cadmium red pigments, but maybe detrimental to thestability of others, particularly to opacifying agents such as titaniumdioxide white opacifier. In referring to alkali metal fluoride andalkali metal oxide I of course mean the compounds of those alkali metalshaving an atomic weight below 40.

Generally it is preferred to utilize sodium-as the only alkali metalconstituent, although lithexample, cobalt oxide may be present if a blueglaze is desired.

In preparing my-improved glaze compositions no special precautions arenecessary except to ium and potassium oxides and fluorides, eitherinsure complete dissolving of the zirconium di- I alone or in admixturewith other of the specified oxide, as evidenced by the clarity of themelt. alkali metal compounds, may be used. By virtue The batch isprepared by selecting raw materials of the relative cheapness'of itscompounds, as which, when melted, will introduce the constituwell as tosecure perfect matching of expansion ents given in the calculatedcomposition of my coefilcient with commercial glasses, I prefer toimproved enamels as tabulated in Table I. Thus, use sodium fluoride andsodium oxide as the preraw materials which decompose to yield oxides orferred alkali metal constituents of my glaze comfluorides in the meltare selected. While the positions. fluorine is represented as alkalimetal fluoride, It 'is preferred to have present in the low- .thefluorine may of course be introduced as lead melting enamel compositionsof high alkali refluoride, or in the form of other fluorine comsistancea certain percentage of boric oxide, not pounds; 4 exceeding 10% byweight based on the total The batch composition is melted to a clear,weight of the composition, for, surprisingly homogeneous liquid, carebeing taken to make enough, within the composition range described, surethat the zirconia is substantially completely amounts of boric oxide upto 10% by weight serve dissolved. To determine this fact, samples of theto render the resulting enamel more resistant to melt may be taken fromtime to time and exthe action of acids. However, where resistivityamined to insure a clear, homogeneous charto the action oi acids is ofno particular impar- 'acter. The molten mass is then fritted, either bytance, boric oxide may be omitted from my impouring into water orotherwise. In accordance proved glaze composition. If augmented resis-.with the usual practice, the frit composition is tivity to the action ofacids is essential, as under then milled, either in a ball mill orotherwise, in certain circumstances the resistivity of the glaze orderto secure the-finely ground base g'lazecomto the action of both alkalineagents and acids position. During the milling pigmentary matemustbeincreased, I prefer to include from 1 to. rials. and/or .opacifyingagents may be added, if 5% of titanium dioxide (Tioz), the amount beingthe resulting glaze composition is to becolored by based on the Fatal Ofthe glaze or Qpaque of the usual opacifying agents composition. Thetitania as is now understood may of course be used, either t titanium u.in the art, must be melted in with the glaze comoxide previously e ifi dor other-agents added posmooto form a clear d homogeneous l in the millto produce opacity. The 'improved 3;; gi prgpa'ration of the i ofiderglazes may contain other addition agents and g 31 is 3:; otheringredients normally present in glaze com- 23 3 c en nc v y 8 ac 1 npositions intended for application to glassware Additional oxidicingredients may be present article l 8 As examples of batch compositionswhich may in my lmproved.gla.ze compositions For exam be melted andfritted to produce-my.improved cadmmm oxlde m amounts up to 5% be glazecompositions, Table II lists the various conpresent in order to promotethe brightness of H t d th t h h ul b cadmium red pigments ifsuch'pigments are press 1 i an 6 m S w m P d e ent. Such addition ofcadmium oxide to the ent in sixteen typical batch compositions. In tlnsflux batch of a 1ead bearmg flux for the purpose 4.5 table all partsgiven are by weight. It should be f promoting brightness of cadmium redunderstood, of course, that I am not limited to ments has b knownin theart since t these ingredients as sources of the various oxides closureof Huber and Felton in U. S. Patent P t in my improved g es, but mayutilize 1,673,679. Other oxides may be added to the th omp u ds wh n td.- wi l yield batch before melting for special purposes as,. for thedesired oxides.

I TABLEII Batch compositions Batch Batch Batch Batch Batch Batch BatchBatch Batch Batch Batch Batch Batch Batch Batch Batch 1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 Redlead.Pb3O4. 43.3 40.5 40.8 37.2 37.8 52.4 42.437.5 42.8. 37.2 42.5 40.6 47.4 48.7 43.4 43.4 Flint, '0, 28.8 31.8 20.118.6 25.2 23.2 21.2 25.0 21.5 24.9 Y 24.2 23.3 35.3 23.7 24.8 24.8'Sodium zirconium silicate,(14% N820, 29% Si02, %21'04) a 7 4.0 14.8 12.410.1 6.1 11.4 11.2 11.4 11.2 10.3 9.0 5.4 7.0 9.0 10.0 Sodium fluoride,

NaF 2.4 4.6 5.4 3.7 0. 1.3 3.2 63 3.2 6.2 6.1 6.4 5.8 68 Sodiumcarbonate,

8,00, 5.8 5.8 1.3 3.7 1.7 4.8 1.6 3.2 1.5 1.-7 7.0 'Lithium carbonate,LhCO; 0-9 2.2 Potassium caronate, 2KC03.3H20- 2-2 Boricacld, H.130. 5.8.8.1 12.1 17.3 10.1 5.3 12.7 11.2 12.0 .2 3 5 12.8 5.6 8.7 8.7 Tltamiumdioxide,

T10, 2.9 2.6 3.0 4.3 5.0 4.3 4.4 5.0 4.3 4.2 3.2 3.4 2.8 4.3 -44 Cadmiumoxide,

CdO 4.3 2.6 3.0 2.8 3.8 3.9 3.2 2.8 2.8 2.7 2.6 1.0 1.0 0.0 2.8 Ammoniumbifluoride, NH4HF,

1.2 1.2 3.1 Lead fluoride,

rim.-. 4.2

tion comprising lead oxide, silica, zirconium dioxide, and an alkalimetal fluoride selected from the group which consists of the fluoridesof lithium, sodium, and potassium; said zirconium dioxide being presentin amounts ranging from 1 to 9% by weight based on the total weight ofTeen: III

Calculated melted flux compositions produced by melting the batcheslisted in Table II Flux Flux Flux Flux Flux Flux Flux Flux Flux FluxFlux Flux Flux Flux Flux Flux 1 2 3 4 5 6 7 8 9 l0 ll 12 13 14 15 16 Aspreviously stated, although no rigid specifications as to melting timeand temperature are required in preparing my glaze compositions, it isnecessary to'conduct the melting under conditions such that asubstantial part, preferably substantially all, of the zirconiumcompounds dissolve in the melt. Undissolved zirconia is not necessarilydetrimental, since the undlssolved portion suspended in the melt acts asan opacifier,

if'opaque enamels are being prepared, but uncadmium sulfide. This yieldsa yellow] glass enamel suitable for application to articles of glasswareto be decorated. By actual test this enamel remained on the glasswarearticle under the attack of strong alkali approximately 50% longer thana similar enamel composition of a type now known to the art having acomparable maturing temperature.

Similarly, a white glass enamel composition highly resistant to theaction of alkaline agents may be prepared by milling ninety parts offlux 8 with-ten parts of titanium dioxide opacifying agent. Glassarticles decorated with this white glass enamel, when subjected to theaction of strong alkalies,- especially at elevated temperatures,retained the white decorative enamel coating for approximately 50%longer than a similar commercially obtainable glaze of comparablematuring temperature.

To those skilled in the art, many modifications and widely differentembodiments of my invention in the general field of decorating ceramicarticles will be readily suggested. The invention is therefore not to berestricted to the precise proportions, procedures, or conditions givenherein as illustrative of my preferred embodiments, but its scope is tobe construed in accordance with the prior art and appended claims.

I claim:

1. An alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating. said glaze composisaid glaze composition,and being melted into said glaze composition as a homogeneousconstituent thereof.

2. An alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating, said glaze composition comprising leadoxide, silica, zirconium dioxide, an alkali metal fluoride selected fromthe group which consists of the fluorides of lithium, sodium, andpotassium, and an alkali metal oxide selected from the group whichconsists of the oxides of the metals lithium, sodium, and potassium,said zirconium dioxide being present in amounts ranging from 1 to 9% byweight, based on the total weight of said composition, and being meltedinto said composition-as a homogeneous constituent thereof.

3. An alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150" F. to a glossy,decorative surface coating, said glaze composition comprising leadoxide, silica, sodium oxide, zirconium dioxide, and an alkali metalfluoride selected from the group which consists of the fluorides oflithium, sodium, and potassium, said zirconium dioxide being present in,amounts ranging from 1 to 9% by weight, based on the total weight ofsaid glaze composition, and being melted into said glaze composition asa homogeneous consituent thereof.

4. An alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating, said glaze composition comprising leadoxide, silica, boric oxide, zirconium dioxide, an alkali metal fluorideselected from the group which consists of the fluorides of lithium,sodium, and potassium, and an alkali metal oxide selected from the groupwhich consists of the oxides of lithium, sodium, and

potassium, said zirconium dioxide being present in amounts ranging from1 to 9% by weight, based on the total weight of said glaze composition,and being melted into said glaze composition as a homogeneousconstituent thereof.

5. An alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150" F. to a glossy,decorative surface coating, said glaze composi tion comprising leadoxide, silica, boric oxide, sodium oxide, zirconium dioxide, and analkali metal fluoride selected from the group which consists of thefluorides of lithium, sodium, and

potassium, said zirconium dioxide being present in amounts ranging from1 to 9% by weight, based on the total weight of said glaze composition,and being melted into said glaze composition as a homogeneousconstituent thereof.

-rides of lithium, sodium, and potassium, said zirconium dioxide beingpresent in amounts ranging from 1 to 9% by weight,based on the totalweight of said composition, and being melted into said lead frit as ahomogeneous constituent thereof.

' 7. Apigmented, alkali-resistant, high lead content glaze compositionsuitable for decorating lassware and maturing below about 1150 F. to aglossy, decorative surface coating, said glaze composition comprising aceramic pigment and a lead frit which comprises lead oxide, silica,zirconium dioxide, an alkali metal fluoride selected from the groupwhich consists of the fluorides of lithium, sodium, and potassium, andan alkali metal oxide selected from the group which consists of theoxides of lithium, sodium, and potassium, said zirconium dioxide beingpresent in amounts ranging from 1 to 9% by weight, based on the totalweight of said composition, and being meltedinto said lead frit as ahomogeneous constituent thereof.

I tive surrace coating, said glaze composition com 8. A pigmented,alkali-resistant, high lead con tent glaze composition suitable fordecorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating, said glaze composition comprising a ceramicpigment and a lead glassware and maturing below about 1150 F. to

an opaque, glossy, decorative surface coating,

said glaze composition comprising an enamel,

opacifying agent and a lead frit which comprises lead oxide, silica,zirconium dioxide, and an alkali metal fluoride selected from the groupwhich consists of the fluorides of lithium, sodium, and potassium, saidzirconium dioxide being present in amounts ranging from l'to 9 byweight, based on the total weight of said composition, and being meltedinto said lead frit as a homogeneous constituent thereof.

10. An opaque, alkali-resistant, high lead content glaze compositionsuitable for decorating glassware and maturing below about 1150 F. to anopaque, glossy, decorative surface. coating,

said glaze composition comprising an enamel opacifying agent and a' leadfrit which comprises lead oxide, silica, zirconium dioxide, an alkalimetal fluoride selected from the group which consists of the fluoridesof lithium, sodium, and potassium, and an alkali metal oxide selectedfrom the group which consists of the oxides of lithium, sodium, andpotassium, said zirconium dioxide being present in' amounts ranging from1 to 9% by weight, based on the total weight of said composition, andbeing melted into said composition as a homogeneous constituent thereof.

11. An opaque, alkali-resistant, high lead content glaze compositionsuitable for decorating glassware and maturing below about 1150 F. to anopaque, glossy, decorative surface coating, said glaze compositioncomprising an enamel opacifying agent and a lead frit which compriseslead oxide, silica, zirconium dioxide, boric oxide, an alkali metalriuoride selected from the group which consists of the fluorides oflithium, sodium, and potassium, and an alkali metal oxide selected fromthe group which consists of the oxides of lithium, sodium, andpotassium, said zirconium dioxide being present in amounts ranging from1 to 9% by weight, based on the total weight of said composition, andbeing melted into said lead frit to form a homogeneous constituentthereof.

12. An alkali-resistant, high lead content glaze composition suitablefor decorating glassware and maturing below about 1150" F. to a glossy,decoraprising lead oxide mamounts ranging from 35 to 55%, silica inamounts ranging from 25 to 40%, zirconium dioxide, and analkali metalfluoride selected from the group consisting of the fluorides of lithium,sodium, and potassium, said zirconium dioxide being present in amountsranging from 1 to 9% as a melted-in, homogeneous constituent of saidglaze, all said percentages being by weight, based on the total weightor said glaze composition.

'13. An alkali-resistant, high lead content glaze composition suitablefor decorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating, said glaze composition comprising lead oxidein amounts ranging from 35 to 55%, silica in amounts ranging from 25 to40%, zirconium dioxide, an alkali metal fluoride selected from the groupwhich consists of the fluorides or lithium, sodium, and potassium, andan alkali metal oxide selected from the group which consists of theoxides of lithium, sodium, and potassium, said zirconium dioxide beingpresent in amounts ranging from 1 to 9% and constituting a melted-in,homogeneous constituent of said glaze composition, all said percentagesbeing by weight, based on the total weight of said glaze composition.

14. An alkali-resistant, high lead content glaze composition suitablefor decorating glassware and maturing below about llbU" F. to a glossy,decorative surlace coating, said glaze composition comprising lead oxidein amounts ranging from 35 to 55%, silica in amounts ranging irom 25 to40%. boric oxide, zirconium dioxide, an alkali metal fluoride selectedfrom the group which consists or the Iluorides or lithium, sodium, andpotassium, and an alkali metal oxide selected from the group whichconsists of the oxides of lithium, sodium, and potassium, said zirconiumdioxide being present in amounts ranging from 1 to 9% as a homogeneous,melted-in constituent of said glaze composition, all said percentagesbeing by weight, based on the total weight of said glaze composition.

15. alkali-resistant, high lead content glaze composition suitable fordecorating glassware and maturing below about 1150 F. to a glossy.decorative surface coating, said glaze composition comprising lead oxidepresent in amounts ranging from 35 to 55%, silica present in amountsranging from 25 to 40%, zirconium dioxide present in amounts rangingfrom1 to 9%, and an alkali metal fluoride selected from the group whichconsists of the fluorides of lithium, sodium, and potassium present inamounts ranging from 1 to 9 said zirconium dioxide constituting ameltedin, homogeneous constituent of said glaze, all said percentagesbeing by weight, based on the total weight of said glaze composition.

16. An alkali-resistant, high lead content glaze composition suitablefor decorating glassware and maturing below about 1150 F. to a glossy,decorative surface coating, said glaze composition having th followingcalculated composition:

Per cent Lead oxide 35-55 Silica 25-40 Zirconium dioxide 1- 9 Alkalimetal fl rid 1- 9 Alkali metal oxide said alkali metal compounds beingthose of an alkali metal having an atomic weight below 40, and saidzirconium dioxide being melted in, together with the other ingredientscomprising said lead glaze composition.

1'7. An alkali-resistant, high lead content glaze composition suitablefor decorating glassware and maturing below "about 1150 F. to a glossy.decorative surface coating, said glaze composition having the followingcalculated composition:

Per cent Lead oxide 35-55 Silica 25-40 Zirconium dioxide 1- 9 Alkalimetal fluoride 1- 9 Alkali metal oxi 0- 5 Boric oxide 0-10 said alkalimetal compounds being those of an Per cent Lead oxide 35-55 Silica 25-40Zirconium dioidde 1- 9 Alkali metal fluoride 1- 9 Alkali metal oxide 0-5 Boric oxide 0-10 said alkali metal compounds being those of an alkalimetal having an atomic weight below 40, and said zirconium dioxideconstituting a meltedin constituent of said lead frit.

19. An opaque, alkali-resistant, high lead content glaze compositionsuitable for decorating glassware and maturing below about 1150 F. to aglossy, decorative surface coating, said glaze composition comprising anenamel opacifying agent and a lead frit having the following calculatedcomposition:

Per cent Lead oxide 35-55 Silica 25-40 Zirconium dioxide 1- 9 Alkalimetal fluoride 1- 9 Alkali metal oxide 0- 5 Boric oxide 0-10 said alkalimetal compounds being those of an alkali metal having an atomic weightbelow 40, and said zirconium dioxide constituting a meltedin constituentof said lead frit.

20. A decorated glassware article decorated with the glaze compositiondefined in claim 1. ALDEN J. DEYRU'P.

CERTIFICATE oi connfichon; Patent Ho.- 25358,'099.' Januar LL; 191m.

mm JIDEYRUP;

It ia-hreby' cartiflgn mat e'rroi' fippegrs'inthe prinfied'sfiecification of'thp aboio hampered pitent rjeqiziring c orrctiggp a s follow: iage 1, firs-t column, line 23, for-ienm ned" read---e n gmg1'-.-; page 5," Table II, Batc1 1-5, oppqaite sodiumflupriqeyllgfi"; for 6." read -'.-6'.3--; and that th qsaid Letters.Patent should. re'dwiththis 'qrrecuon therein that the same may confdrmho tfl e z 'ecord 61" the casbj inuthg' Pgte'nt-btfl I Signed andsaalqdft hi'a 15th. as; 01' rebiugr b. 191 1;.

Van Aradale, (89 kht'i-ng -coqimi sgionpr nf Patents.

